Internal combustion engines have exhaust manifolds coupled to exhaust pipes. The exhaust pipes generally have several discontinuities to allow the exhaust pipe to be routed around various components on the underbody of a vehicle. A discontinuity is defined as any variation in the dimensions or shape of an exhaust system which affects the flow path of exhaust gases. For example, a discontinuity can be: (i) a bend in an exhaust pipe, (ii) an irregular flow path surface at a coupling between two exhaust pipe sections, (iii) a change in the diameter of an exhaust pipe section, (iv) an emission control device restricting flow therethrough, or (v) any other flow restriction in the exhaust pipe portion.
The inventors herein have recognized that undesirable impingement noise is generated by the exhaust gas pulses contacting discontinuities in conventional exhaust systems. Further, the inventors herein have recognized that it would be desirable to utilize a noise attenuation device upstream of an exhaust system discontinuity to reduce impingement noise in an exhaust system.